At an activity level of 9,600 machine-hours in a month, Montgomery Corporation's total variable production engineering cost is $402,336 and its total fixed production engineering cost is $570,240. What would be the total production engineering cost, both fixed and variable, at an activity level of 9,900 machine-hours in a month? Assume that this level of activity is within the relevant range. Select one: O a. $101.31 O b. $99.78 O c. $99.51 O d. $98.24